Fuel duels - Fuel cell

As used in: A few prototypes are running, but that's it so far.

What is it? By combining hydrogen and oxygen in the fuel cell, it produces power to run an electric motor, which drives the car.

Where can I buy it? Nowhere yet, but fuel-cell cars are expected to be on sale within 10 years.

Pros: Fuel-cell power has zero emissions, except water. It is not reliant on fossil fuels.

Cons: There is no supply infrastructure yet and hydrogen must be carried at high pressure in large, heavy tanks.

Expert view: This is widely thought to be the fuel of the future but there are major problems over the large-scale manufacture of hydrogen, as well transport and storage.

Outlook: This seems the most promising alternative fuel but, given the problems to overcome, it's a long-term solution.